FITTING AS 4264044 - Caterpillar

Illustration 1 g00368872
Schematic of Main Hydraulic System in RAISE Position (1) Main control valve. (2) Small pump section. (3) Large pump section. (4) Quick-drop valve (left). (5) Line from the main control valve. (6) Line from the main control valve. (7) Quick-drop valve (right). (8) Tilt valve spool. (9) Relief valve for lift circuit. (10) Dump valve for lift circuit. (11) Chamber. (12) Load check valve for lift circuit. (13) Outlet to hydraulic oil tank. (14) Passage to rod end of lift cylinders. (15) Passage to head end of lift cylinders. (16) Lift valve spool. (17) Lift cylinder (left). (18) Lift cylinder (right). (AA) Oil from large pump section. (BB) Oil from small pump section. (CC) Return oil.The main hydraulic system consists of the following components: Main control valve (1), Small pump section (2), Large pump section (3), Quick-drop valve (left) (4), Quick-drop valve (right) (7), Lift cylinder (left) (17) and Lift cylinder (right) (18) .The operator of the machine controls the lift function of the machine with a mechanical link. The mechanical link is connected from the control lever in the cab to main control valve (1). The mechanical link is a cable.Lift valve spool (16) has four positions: RAISE, HOLD, LOWER and FLOAT.Lift valve spool (16) is manually operated by the control lever. Movement of the lever to the rear sends pressure oil to the rod end of the lift cylinders and the blade raises.When the control lever is moved forward, pressurized oil is sent to the head end of the lift cylinders. This causes the blade to lower.When the operator pushes the lever past the LOWER position, the lever will go into the FLOAT position. The FLOAT position is the only position with a detent.In the FLOAT position, the blade is free to move up or down according to the outside forces.Oil from the large section of the pump flows into chamber (11). When the oil flows into chamber (11), oil mixes with the oil from the tilt circuit.RAISE Position
When lift valve spool (16) is moved to the RAISE position, the pressure of the pump oil in chamber (11) increases and opens load check valve (12) .When load check valve (12) opens, the spring in dump valve (10) has more force than the pump oil in chamber (11) .The spring moves dump valve (10) which closes the holes in the dump valve. Now, the pump oil can not flow through the dump valve to the hydraulic oil tank.The pump oil flows through load check valve (12). Next, the oil flows around lift valve spool (16) and into passage (14). The oil then flows through line (6) to the inlets of quick-drop valves (4) and (7). The oil then flows through the quick-drop valves to the rod end of the lift cylinders.The rod end of the lift cylinders are connected to the blade. The pump oil from passage (14) in the rod end of the lift cylinders moves the pistons and rods farther into the cylinders